There have been developed surface light-emitting devices employing solid state light-emitting elements such as LEDs (Light Emitting Diode) as point light-sources.
Recently, such surface light-emitting devices employing point light-sources are used as backlights in display apparatuses such as liquid crystal TVs and liquid crystal monitors and as lighting equipment etc.
In general, surface light-emitting devices employing point light sources are tend to exhibit luminance unevenness because the light sources are point-like. Accordingly, various ingenuities are required in order to make luminance at the light-emitting surface even. For example, Patent Literatures 1 and 2 disclose surface light source devices designed such that light flux control members are provided at light-emitting surface sides of light-emitting elements (point light sources) in order to control angles of beams of light emitted from the light-emitting elements and smoothly broadening emitted light flux in a wide range, so that the beams of light from the light-emitting elements are more likely to be mixed with each other and luminance of emitted beams of light become even, thereby overcoming luminance unevenness.
In the surface light source device disclosed in Patent Literature 1, as shown in FIGS. 14(a) to 14(c), a light-emitting device (light-emitting element module) is designed such that a flat portion at a back surface 102a of an light flux control member 102 is attached and fixed to a fixing substrate 104 of a light-emitting element 101. Consequently, the light-emitting element 101 is completely covered with the light flux control member 102. This raises a problem that heat from the light-emitting element 101 is difficult to be released.
In order to deal with this problem, in the surface light source device disclosed in Patent Literature 2, as shown in FIG. 15(a), a light-emitting device (light-emitting element module) is designed such that a flat portion at a back surface 102a of an light flux control member 102 is fixed to a fixing substrate 104 of a light-emitting element 101 via a plurality of columnar members 105. This structure allows securing a space for releasing heat around the light-emitting element 101.
Japanese Patent Application Publication, Tokukai, No. 2006-324256 (published on Nov. 30, 2006)
Japanese Patent Application Publication, Tokukai, No. 2009-117207 (published on May 28, 2009)